His theory arose from his observations of a Wisconsin-based flying saucer cult of the 1950s whose prophecy of universal destruction failed to come true. The cult, led by Lake City, Utah resident Marian Keech [1], prophesied a vast flood would soon kill everyone on Earth except for the members of the cult, who would be carried away by flying saucers. Before the predicted flood, the cult was very secretive and very reluctant to speak to the media or make converts. After the predicted flood, they stopped being secretive and spoke very eagerly to the media.

Festinger explained this transformation as occurring because the prediction failed: there was no global flood and no flying saucers arrived to carry the cult to salvation. The cult was ridiculed, and though they had an explanation for the failure of their prophecy -- on the night in question their prayers "had spread so much light that God saved the world from destruction" -- nobody took it seriously. This is why Festinger suggested that the cult became fervently evangelistic. The only way for them to reverse their humiliation was to convert other people to their beliefs. If everyone believed, no one would laugh. However, this did not work: after such a spectacular failure, the cult predictably failed to convert anyone. For further information on the cult and its behavior, see Festinger's book When Prophecy Fails and the website "When Prophecies Fail".

Festinger also proposed social comparison theory, according to which people evaluate their own opinions and desires by comparing themselves with others.